Abstract

Sixteen strains of Salmonella were isolated from clinically diagnosed
diarrhea patients. They were tested against a range of antimicrobial agents, and
typed by serological test and RAPD fingerprinting. All the strains have the
similar pattern of antimicrobial susceptibility. The serological test has typed
them into 3 serovars but the RAPD fingerprinting has classed them into 2 major
clusters. Three strains of bifidobacteria were analyzed for their survival rate in
human stomach condition. It showed that the ability of bifidobacteria to survive
was strains dependant. Bifidobacterium pseudocatanulatum F117 and
Bifidobacterium infantis can survive at pH value of human stomach after
exposure for 90 minutes but not Bifidobacterium pseudocatanulatum G48. The
survival of bifidobacteria was higher in the pH after meal compared to the pH
before meal (fasted state). The dose effect study demonstrated, that the initial
concentration of bifidobacteria would affect the duration of inhibitory activity against Salmonella. Lower initial concentration exhibit greater inhibitory activity.
The inhibition of Salmonella was due to the production of acetate and lactate by
bifidobacteria and the effectiveness was higher at low pH. Acetate and lactate
production was excessive when the initial concentration of bifidobacteria was
low due to the high growth rates, metabolism, and competition of energy sources.